In that case you look up when the next train to your destination is, and take that train.
What kind of tickets did you buy? And where? For what route?
Tickets are normally for a route, not a train. A ticket allows you to make one trip from the origin to the destination, on the day of validity. And that using a train or trains, of your choice. You are not limited to the schedule you selected during booking.
Discounted tickets (supersaver tickets) however do come with limitations. These tickets will have printed on them which trains you are supposed to take. But if you miss a connection due to a late previous train you can just take the next available train, without having to do anything special. Trains usually run every half hour.
And even with a wheelchair transfers can be quick, as most trains are low floor nowadays.